Field of the Invention
The invention relates to a permanent magnet rotor and a motor using the same.
Description of the Related Art
With increasingly requirements of the air-conditioner technology for noise, vibration and energy conservation, requirements for motors are correspondingly increased, and thus motors driven by sine wave with small noise and vibration are used by more and more users.
To implement sine wave drive, a rotor is to generate a sine wave magnetic field. A normal measuring method is to enable the rotor to rotate whereby generating counter-electromotive force via a stator winding and detecting output a waveform in a power-off state, and a waveform of a magnetic field generated by the counter-electromotive force plays an important role in controlling sine wave. In a motor made of ferrite tiles with a weaker magnetic field, distortion of the sine wave has little effect on controlling, but in a strong magnetic field generated by sintered silicon carbidendfeb, experiments have indicated that if a waveform of the counter-electromotive force is not matched with driving sine wave generated by controlling, obvious vibration of the motor may occur.
Conventionally, there are several method of enabling the rotor to generate a sine wave magnetic field: a first one is a combination of special teeth and the pole number, for example, a stator uses ten wire receiving grooves, and a rotor uses a magnetic tile with nine poles, or the rotor uses 12 wire receiving grooves, and the rotor uses a magnetic tile with ten poles, or the rotor uses nine wire receiving grooves, and the rotor uses 8 poles. FIG. 1 illustrates a waveform of counter-electromotive force of a motor using these combinations between the special teeth and the pole number, a curve of the waveform of the counter-electromotive force of the motor is smooth, and there is no distortion point on the curve. The waveform features good effect for sine wave control. However, wire winding of the special tooth is very complex, and the wire winding of the coil winding comprises forward coil winding and reverse coil winding, which feature poor manufacturability, and comparatively low motor efficiency; a second one comprises: under a ratio between the number of teeth and the pole number of 3:2, magnetic tiles are designed to be eccentric, and are circumferentially distributed and attached to the surface of the motor. FIG. 2 illustrates counter-electromotive force of the coil winding, a waveform of the counter-electromotive force of the motor is like sine wave with large distortion. As being driven by the sine wave, the motor has large vibration and noises, which causes advantages of the sine wave motor not to be embodied, results in large eccentricity of the magnetic tile, and increases cost of the magnetic tile.